Compressible primer contact and fixed firing pin assembly

ABSTRACT

A compressible primer contact plug and fixed firing pin assembly combination for use in small caliber electrically actuated caseless ammunition and small arms weapons. The primer contact is operationally interposed between a priming mixture and a firing pin or center electrode which is an integral part of a small arms weapon bolt assembly and is affixed thereto. Undesirable propellant gas leakage is obviated in the firing pin area by the fixed firing pin bolt assembly which acts as an obturator during the ballistic cycle. The primer contact plug is located slightly below flush with respect to the rear surface of the caseless cartridge and from that position, tolerates longitudinal compression to assure good electrical conduction to the sensitive priming mixture while compensating for variations in the seating depth of the primer assembly.

United States Patent Perkins et al.

in] 3,714,728 [45] 'Feb. 6,- 1973 1 COMPRESSIBLE PRIMER CONTACT ANDFIXED FIRING PIN ASSEMBLY [75] Inventors: William E. Perkins,'Runnemede, N.J.; Allen F. Schlack, Churchville; Thomas Q. Ciccone,Langhome, both of Pa.

[73] Assignee: The United'States of America as represented by theSecretary of the Army [22] Filed: Dec. 22, 1970 21 Appl. No.: 100,742

[52] U.S. Cl ..42/84, 102/46, l02/DlG. 1 [51] Int. Cl ..F4lb 5/18 [58]Field of Search ...42/84; 89/26, 28, 135; 102/46, lO2/D1G. l

[56] References Cited UNlTED STATES PATENTS 365,842 7/1887 Monfort..102/46 1,485,404 3/1924 Martin et a1 ..102/46 3,613,282 10/1971 Ramsay..42/84 3,577,922 5/1971 Zehfeld et a1. ..102/46 712,826 11/1902 Mason..102/46 Primary Examiner-Stephen C. Bentley Attorney-Edward .1. Kelly,Harry M. Saracovitz, Herbert Her] and Sheldon Kanars [57] ABSTRACT Acompressible primer contact plug and fixed firing pin assemblycombination for use in small caliber electrically actuated caselessammunition and small arms weapons. The primer contact is operationallyinterposed between a priming mixture and a firing pin or centerelectrode which is an integral part of a small arms weapon bolt assemblyand is affixed thereto. Undesirable propellant gas leakage is obviatedin the firing pin area by the fixed firing pin bolt assembly which actsas an obturator during the ballistic cycle. The primer contact plug islocated slightly below flush with respect to the rear surface of thecaseless cartridge and from that position, tolerates longitudinalcompression to assure good electrical conduction to the sensitivepriming mixture while compensating for variations in the seating depthof the primer assembly.

6 Claims, 6 Drawing Figures Mitchell ..102/46 PATENTEDFEH 6 I9753,714,728

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INVENTORSI ALLEN F. SCHLACK WILLIAM E. PERKlNS THOMAS Q.C.\CC.ONE

DY "23,1? M HMWATTJLZZNEY5 COM PRESSIBLE PRIMER CONTACT AND FIXED FIRINGPIN ASSEMBLY The invention described herein may be manufactured, used,and licensed by or for the Government for governmental purposes withoutthe payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to an electricalprimer for actuation of caseless ammunition and more particularly to aprimer contact plug that allows electrical ignition of a priming mixturewhile effectively prohibiting the undesirable leakage of propellantgases.

Generally there are two approaches that can be taken to actuatecombustible ammunition; mechanically, using percussion primers orelectrically, using electric primers. Design and performance problemshave been encountered in both approaches but only the latter is to behere considered.

Electric primers usually consist of two electrodes a center contact as apositive pole and an outer contact cup as a negative pole or groundseparated by an insulator with a bridge wire, graphite bridge orconductive mix to provide a conductive path between the positive andnegative poles. In communication with this conductive path and betweenthe two poles is charged a heat or voltage sensitive priming mix whichis ignited when electrical energy is applied.

I-Ieretofore with regard to electrically primed ammunition, the primerwas inserted below flush to prevent ignition by an accidental voltageapplication. Because of the tolerance allowed for the seating depth ofthe primer, coupled with the tolerances of an operational weapon, thefiring pin (center electrode) must have been extendable from the boltface and must have had the degree of freedom to overcome the combinedaforementioned tolerances to thereby assure good electrical contactbetween the center electrode and the primer contact.

The use of a moveable firing pin in electrically fired weapons usingcased ammunition has presented no major problem. With caselessammunition, however, a moveable firing pin does present a major problemsince propellant gases can leak around the moveable firing pin tocorrode the electrical insulation between the firing pin and the boltand also corrode the pin movement assembly. Obturators have been usedbut with limited success in preventing leakage of the high pressuredpropellant gases past the firing pin.

Moreover, fixed firing pins have been successfully utilized withcaseless ammunition due to the tolerances of the seating depth of theprimer. However, the use of fixed firing pins is desirable. It is alsodesirable to prevent this gas leakage to assure a durable and morereliable weapon, and to assure more consistent projectile ballistics.

It is therefore the general purpose of the present in vention toreliably ignite a priming mixture by application of a voltage whileeffectively prohibiting the leakage of propellant gases past firing pinfixed with respect to the bolt.

SUMMARY OF THE INVENTION The use of a compressible primer contact plugin protruding from the bolt face, thus preventing the leakage ofpropellant gases in the firing pin area. The firing pin is electricallyinsulated from the bolt.

To assure good electrical connection between the firing pin and theprimer,,the primer contact is constructed of an electrically conductivecompressible material. This compressible primer contact is seated onlyas far below flush as will allow tolerable compression thereof whilestill assuring good electrical contact.

The primer contact, in one embodiment, may be constructed of a solidcore of rubberized propellant having means for electrical conductionbetween the caseless ammunition allows the weapon firing pin I (centerelectrode) to be fixed in a position slightly two conductive end layersof the core. Alternatively, the primer contact may be constructed from ahollow cylinder of consumable material having bellows or accordian-likesidewalls and rigid conductive end layers or rigid sidewalls and atleast one flexible conductive end layer both of these constructions alsohaving means for electrical conduction between the two conductive endlayers.

In the operation of a typical embodiment of this invention, a round ispushed forward by the bolt assembly until the cartridge is firmly lodgedin the chamber. The foremost part of the bolt assembly, the firing pin,compresses the primer contact (positive poles) until the bolt facecontacts the outer annular position (negative pole) of the primer. Whenthe trigger circuit is closed, electrical current flows through thecenter electrode to the primer contact, through the heat sensitive andconductive priming mixture to the propellant container, then back to thebolt (ground electrode).

Current passing through the heat sensitive and conductive primingmixture generates resistive heat which ignites the priming mixture toinitiate the ballistic cycle. During this cycle all the components ofthe primer are combusted so as to leave no harmful residue in the weaponchamber. The bolt with the integral or fixed firing pin acts as anobturator preventing the rearward leakage of the propellant gases in theprimer area, thus contributing to the consistent ballistics of theweapon system.

DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTReferring now to the drawing and more particularly to FIG. I thereof,there is shown a gun chamber 21 which houses a bolt assembly 22, forelectrical actua-' tion of a small caliber caseless cartridge '10 havinga main propellant charge 11. An electrical primer assembly 23 is seatedin the base of the cartridge 10 and consists of an outer conductor cup12, a voltage sensitive priming mixture 14 packed into the bottom of thecup 12 and an annular shaped electrical insulator 15 in communicationwith the internal sidewalls of the cup 12 and extending only as far asthe lip thereof and dimensioned to receive a firing pin therewithin.Outer cup edge 13 must extend slightly rearward of the cartridge base10A to assure satisfactory electrical ground contact. A plug ofconductive rubberized propellant primer contact 16 such as a graphiteadded or lead dioxide added to rubberized propellant fills the remainderof the cup 12 and communicates with the annular insulator 1S and thepriming mixture 14. As shown, the primer contact 16 is in asemi-compressed state, the compressive force being applied by the boltassembly 22.

Bolt assembly 22 incorporates a firing pin 19 which functions as apositively poled electrode and which is insulated by an insulator seal18 from a negative electrode 17 which is configured to communicate withthe interval sidewalls of the gun chamber 21. The firing pin 19 is fixedto the bolt assembly 22 and is encased thereby except for a portionwhich protrudes from the bolt face 20 and operationally bears upon theprimer contact 16.

The primer contact plug described heretofore is illustrative only, manyvariations being realizable in light of the invention. Such variationsare shown in FIG. 2A 2E inclusive, where there is shown modifications ofthe primer contact plug illustrated in FIG. 1. A core of nonconductiverubberized propellant 25 having conductive end layers 26 and means forelectrical conduction between the end layers such as a combustible metalwire 27 of FIG. 2A, a bridge of combustible conductive material 28 suchas lead dioxide or zirconium of FIG. 2B or conductive outer layer 29 ofFIG. 2C. Another modification of the primer contact plug as illustratedin FIG. 1 is shown in FIG. 2D. There is shown hollow cylinder 30 withbellows-like sidewalls (which in compression collapse much like thebellows of an accordian) having rigid conductive end layers 34 at rightangles thereto and the aforementioned combustible metal wire 27 forelectrical conduction between the rigid end layers.

A further modification of the invention illustrated in FIG. 1 is shownin FIG. 2B wherein a cup-shaped rigid consumable material 31 is encasedwithin a like cupshaped outer conductive layer 32 to form a plug whichis capped by a flexible conductive lid 33; upon compression, only lid 33is deformed, the cup-shaped members remaining rigid.

The operation of the invention will now be explained. When caselesscartridge is firmly lodged in the gun chamber 21 firing pin 19compresses the primer contact 16 (or any of the primer contacts shown inFIGS. 2A 2E, inclusive) until ground electrode face contacts the outeredge 13 of primer conductor Propellant gases are prevented from leakingrearward in the firing pin area by the fixed firing pin-bolt assembly22. There being no gas leakage in the primer area, the output of theprimer is fully utilized to ignite the propellant and thus provide moreconsistent ballistics.

It has thus been shown that this invention reliably ignites anelectrically sensitive priming mixture while effectively prohibiting theleakage of propellant gases past the firing pin.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

We claim:

1. In combination with a priming mixture within a primer assembly and afixed firing pin bolt assembly for the actuation of a caseless, smallcaliber electric cartridge, the improvement comprising an electricallyconductive compressible primer contact assembly operationally interposedbetween said bolt assembly and said priming mixture for compression bysaid bolt assembly until said bolt assembly abuts said cartridge tothereby prevent, upon the initiation of the ballistic cycle, the flow ofpropellant gases rearward in the firing pin area of said bolt assembly,said primer contact including a plug of rubberized propellant and a leaddioxide bridge extending therethrough.

2. In combination with a priming mixture within a primer assembly and afixed firing pin bolt assembly for the actuation of a caseless, smallcaliber electric cartridge, the improvement comprising an electricallyconductive compressible primer contact assembly operationally interposedbetween said bolt assembly and said priming mixture for compression bysaid bolt assembly until said bolt assembly abuts said cartridge tothereby prevent, upon the initiation of the ballistic cycle, the flow ofpropellant gases rearward in the firing pin area of said bolt assembly,said primer contact assembly including a substantially cylindrical plugof primer contact material, a pair of electrically conductive layerspositioned one each at the respective ends of said plug andsubstantially perpendicular to a central axis thereon, and electricallyconductive means operatively connected to said layers and substantiallyparallel to said central axis for carrying applied current to one ofsaid layers, said plug being a core of rubberized propellant.

3. The structure according to claim 2 wherein a lead dioxide bridgeextends through said rubberized propellant core.

4. The invention according to claim 2 wherein said conductive means isencased by said core.

5. The invention according to claim 4 wherein said conductive means is acombustible metal wire.

6. The invention according to claim 2 wherein said conductive means is aconductive layer in communication -with the external surface of saidcore.

I I I! 1.! l

1. In combination with a priming mixture within a primer assembly and afixed firing pin bolt assembly for the actuation of a caseless, smallcaliber electric cartridge, the improvement comprising an electricallyconductive compressible primer contact assembly operationally interposedbetween said bolt assembly and said priming mixture for compression bysaid bolt assembly until said bolt assembly Abuts said cartridge tothereby prevent, upon the initiation of the ballistic cycle, the flow ofpropellant gases rearward in the firing pin area of said bolt assembly,said primer contact including a plug of rubberized propellant and a leaddioxide bridge extending therethrough.
 1. In combination with a primingmixture within a primer assembly and a fixed firing pin bolt assemblyfor the actuation of a caseless, small caliber electric cartridge, theimprovement comprising an electrically conductive compressible primercontact assembly operationally interposed between said bolt assembly andsaid priming mixture for compression by said bolt assembly until saidbolt assembly Abuts said cartridge to thereby prevent, upon theinitiation of the ballistic cycle, the flow of propellant gases rearwardin the firing pin area of said bolt assembly, said primer contactincluding a plug of rubberized propellant and a lead dioxide bridgeextending therethrough.
 2. In combination with a priming mixture withina primer assembly and a fixed firing pin bolt assembly for the actuationof a caseless, small caliber electric cartridge, the improvementcomprising an electrically conductive compressible primer contactassembly operationally interposed between said bolt assembly and saidpriming mixture for compression by said bolt assembly until said boltassembly abuts said cartridge to thereby prevent, upon the initiation ofthe ballistic cycle, the flow of propellant gases rearward in the firingpin area of said bolt assembly, said primer contact assembly including asubstantially cylindrical plug of primer contact material, a pair ofelectrically conductive layers positioned one each at the respectiveends of said plug and substantially perpendicular to a central axisthereon, and electrically conductive means operatively connected to saidlayers and substantially parallel to said central axis for carryingapplied current to one of said layers, said plug being a core ofrubberized propellant.
 3. The structure according to claim 2 wherein alead dioxide bridge extends through said rubberized propellant core. 4.The invention according to claim 2 wherein said conductive means isencased by said core.
 5. The invention according to claim 4 wherein saidconductive means is a combustible metal wire.